1,1,2-Trichloro-1,2,2-trifluoroethane (F113) has been widely used in industry for cleaning and degreasing highly-varied solid surfaces (metal components, glasses, plastics, composites) for which the absence or at the very least the lowest possible residual content of impurities, in particular of organic origin, is required. F113 was particularly suitable for this use owing to its nonaggressive nature with regard to the materials used. This product was used in particular in the field of the fabrication of printed circuits, for removing the residues of the substances used to improve the quality of the soldered joints (denoted by the term solder flux). This removal operation is denoted in the trade by the term “defluxing”.
Mention may also be made of the applications of F113 in the degreasing of heavy metal components and in the cleaning of mechanical components of high quality and of great accuracy, such as, for example, gyroscopes and military, aerospace or medical equipment. In its various applications, F113 is most commonly used in combination with other organic solvents (for example methanol), in order to improve its cleaning capacity.
F113 is also used in fields, in particular in optics, where it is required to have surfaces which are devoid of water, i.e. surfaces where water is only present in trace amounts undetectable by the measurement method (Karl Fisher method). F113 is, for this purpose, used in operations for drying (or dewetting) said surfaces, in combination with hydrophobic surfactants.
However, the use of F113-based compositions is now prohibited since F113 is one of the chlorofluorocarbons (CFCs) suspected of attacking or damaging stratospheric ozone.
Various solutions have been proposed for providing a replacement for F113, but which does not have the problems of destroying the ozone layer or of increasing the greenhouse effect. The greenhouse effect of a given product is quantified by its GWP (global warming potential) which takes into account the intrinsic effect of absorption of radiation by the molecule, but also the lifetime of the molecule in the atmosphere (or what amounts to its concentration for a considered period of time, most commonly one century). This GWP is given with respect to CO2, taken as reference gas.
Document U.S. Pat. No. 6,770,614 describes compositions to replace F113, comprising in particular 1,1,1,3,3-pentafluoro-butane (365mfc), trans-dichloroethylene (tDCE), an ether such as nonafluoromethoxybutane (HFE7100) or nonafluoroethoxybutane (HFE7200), and also methylal and an alcohol. The amount of pentafluorobutane is described as being from 20% to 55, preferably from 25% to 50% by weight. The amount of trans-dichloroethylene is described as being from 40% to 70%, preferably from 53% to 62% by weight. The amount of ether is described as being less than 20%, preferably from 5% to 15% by weight. The minimum amount of methylal and/or of alcohol is not expressly mentioned, but the examples give an amount of approximately 1% by weight for methylal and approximately 1% by weight for the alcohol (isopropanol). The compositions according to that document have the drawback of being inflammable.
Document WO-A-00/36046 describes quite generally mixtures of pentafluoropentane and fluorinated ether, with optionally an organic solvent. Chlorinated solvents, such as trans-dichloroethylene, can be used as organic solvent.
Application WO-A-0056833 is directed toward cleaning compositions. This application describes mixtures of pentafluorobutane, trans-dichloroethylene and nona-fluoromethoxybutane. The amounts proposed (as % by weight) are in particular 1-98/1-64/1-75. Among the examples of such compositions, a mixture containing, as % by weight, 35% of pentafluorobutane, 64% of trans-dichloroethylene and 1% of nonafluoromethoxybutane is indicated. Application US20050267006, which is a continuation of the previous application, specifically claims quaternary mixtures of pentafluorobutane, trans-dichloroethylene, nonafluoromethoxybutane and isopropanol.
There is still a need for a cleaning composition as a replacement for F113, which is preferably more effective than the prior art compositions, in particular with regard to the precision cleaning and/or degreasing of metal components, and which is preferably non-inflammable and advantageously which remains non-inflammable when used in machines.